So where is the monster BN? All I saw was a normal full grown one. 6" does not make a monster BN - that is still within the range of normal size. To you it may be a monster, I assure you in reality it isn't. I too have a couple that size and so do many other people.
You need to understand that when a size is given, it refers to the customary aquarium-raised size (or AVERAGE size) and not an absolute. That means they may be larger or smaller than sizes listed. Occasionally, a fish will exceed the boundaries greatly and could be considered monster or giant for it's species. When a fish reaches 1-1/2 X the normal size (i.e. listed at 12" but specimen reached 18") then you have a noteworthy fish.